1. Field of the Invention
This invention relates to TV receiver power supplies of the type wherein power to operate the audio output stage is taken from the horizontal output deflection circuit.
2. Description of the Prior Art
The energy supplied to a horizontal deflection circuit must be controllable, and a suitable supply circuit consists, e.g., of a source of dc voltage and a storage inductance.
Horizontal sweep or deflection circuits are known in which, for generating a periodic sawtooth current within the respective deflecting coil of the picture tube, the deflection coil is connected in a first current branch, via a first controlled switch, conductive in both directions, to a sufficiently large dimensioned capacitor serving as the source of current, with the controlled switch being formed by the antiparallel connection of a controlled rectifier with a diode. The control electrode of the rectifier is connected to a source of control pulses by which the switch is rendered conductive during one part of the sawtooth sweep. The controlled rectifier is disconnected by a commutating process, i.e., by a current reversal in the controlled rectifier which is initiated by a second controlled switch.
Moreover, the first controlled switch forms part of a second current branch which, in a series arrangement with the controlled switch, contains a second source of current and a reactance capable of oscillating. The reactance substantially consisting of a coil and of a capacitor, serves to take up energy from the second source of current during a predetermined time interval when the first switch is closed. This energy as taken from the second source of current, corresponds to the switching losses which have incurred during the preceding deflection period.
In the known basic circuit as described hereinbefore, however, it has not been taken into consideration that it is customary to connect to the horizontal final stage also the high-tension transformer necessary for operating the picture tube. With the aid of this conventional circuit, the high-tension necessary for operating the picture tube, is generated in such a way that the horizontal flyback pulses are stepped up to the necessary voltage value by a step-up transformer, with the voltage being supplied to the picture tube via a rectifier arrangement. The high-tension transformer is arranged in parallel with the deflection system. Considering that the energy as taken off the high-tension transformer, in dependence upon the beam current variations, is not constant, the high tension must be correspondingly readjusted owing to the finite resistance of the high-tension source. This means to imply that the energy as supplied to the horizontal final stage must be equal to the already mentioned losses of the deflection circuit itself plus the energy required for operating the tube.
It is also known to obtain the energy required for supplying the audio output stage via a secondary winding of the storage inductance, likewise from the horizontal deflection circuit.
For avoiding, i.e., for stablizing the reactions caused by the changed loading by the audio output stage, upon the picture width of the television receiver, a special stabilization is required in this conventional type of circuit in the supply system for the audio output stage.
This stabilization involves a certain investment in circuitry and, moreover, causes additional power losses.